1. Field of the Invention
The invention relates to suspension drive arrangements for rotary drums and particularly to wire rope suspension mechanisms used to support and to drive rotary kilns, agglomerators and the like.
Cable suspended drums find wide application in installations processing ore, coal, cement and the like wherever rotary motion of a loose, heavy load is needed. In particular, a rotary drum kiln carrying a loose, heavy load has a tendency to warp out of round under its own weight when supported by underlying rollers and drive mechanisms. Such warping can dislodge kiln brick and severely damage the refractory wall. It has been discovered that rotary drums suspended by encircling cables (e.g., chains and wire ropes) are less susceptible to circular deformation because the tension of cable loading surrounding the drum counteracts the flattening tendency of the supported load. The distribution of the load support varies with the degree of loading. One technique for adjusting loading support distribution is through the adjustment of lateral spacing of pairs of overhead sheaves upon which suspension cables are carried.
A cable suspended drum by its nature does not have a positive drive if rotated by powering the overhead sheaves. Rotary traction depends primarily on the loading of the drum. As a consequence, insufficient traction may be present to turn a light drum with a heavy load, particularly at startup. Means must therefore be devised for providing adequate traction between the suspension cables and the sheaves under light load conditions.
A cable suspended drum during rotation has a tendency to sway from side to side with load shifts. Moreover, a loose, agglomerated, or partially ground load tends to "climb" one side of the drum to cause a change in the center of mass. This causes an imbalance of loading on the support cables and accelerated cable wear.
Connector pieces are generally used to connect wire rope ends to permit adjustment and replacement of the endless wire ropes. In corrosive or abrasive environments, a wire rope can be expected to wear most rapidly at its connector piece, and particularly at the juncture of the wire rope with the bridge piece. Furthermore, many connector pieces of the known prior art shorten the effective length of the rope loop upon riding over the curved track of a sheave or drum. The result is increased tension on the wire rope unevenly loading the rope, which consequently accelerates wear.
2. Description of the Prior Art
Typical installations wherein a drum suspended by a chain or wire rope system from overhead sheaves are described in U.S. Pat. Nos. 3,097,834, 3,401,924 and 3,699,433. In the systems therein described, a drum is hung on wire ropes from pairs or multiples of overhead sheaves which are supported above overhead horizontal structural beams. Adjustability of the spacing of the sheaves for the purpose of load distribution is provided by lateral adjustment of the sheave axes on shafts on the horizontal structural beams. Unfortunately, lubrication is difficult, and the tracks must be maintained free of debris in order that the sheaves may move freely on the tracks. Otherwise damage may result to the tracks and to the sheave support rollers. Means are needed to eliminate this possibility of damage and to minimize lubrication requirements.
These known prior art patents also disclose connector pieces and cable adjustment devices which represent the state of the art. In the present application the problems identified are concerns not sufficiently addressed in the known prior art.